Mixed flow grain dryer with vacuum cool heat recovery system

Abstract

A grain dryer having a mixed-flow heating section, a tempering transition section, and a vacuum-cooled crossflow cooling section. A fan positioned on the end of the dryer creates a negative pressure in the cooling plenum that pulls air through the grain, warming the air while cooling the grain. This warmed air is pulled through the fan and then passed through a heater to bring it to appropriate drying temperature. This air is then pushed into a heating plenum, where it passes through a mixed-flow grain column, drying the grain, and then exhausted to ambient air.

What is claimed is: 
     
       1. A grain dryer, comprising:
 a wet holding section in communication with a mixed-flow heating section; 
 a tempering transition section having solid inner and outer walls adapted to prevent air from passing through the tempering transition section in communication with the mixed-flow heating section; 
 a crossflow vacuum-cooling section in communication with the tempering transition section; 
 an unloading section in communication with the crossflow vacuum-cooling section; 
 a negatively pressurized plenum within the crossflow vacuum-cooling section, between the tempering transition section and the unloading section having a fan in communication with a heater; and 
 wherein the tempering transition section is positioned between the mixed-flow heating section and the crossflow vacuum-cooling section and ambient air flows through the crossflow vacuum cooling section, is pulled into the fan, and then further heated by the heater. 
 
     
     
       2. The dryer of  claim 1  further compromising a positively pressurized plenum within the mixed-flow heating section. 
     
     
       3. The dryer of  claim 1  further comprising a discharge port in communication with only one discharge conveyor. 
     
     
       4. The dryer of  claim 1  having a grain distribution baffle within the tempering transition section; wherein the grain distribution baffle is positioned below the mixed-flow heating section and is configured to equalize flow distribution in the mixed-flow heating section and the crossflow vacuum cooling section. 
     
     
       5. The dryer of  claim 1  wherein the heating section is above the tempering transition section and the crossflow vacuum-cooling section is below the tempering transition section. 
     
     
       6. The dryer of  claim 1  further comprising the mixed-flow heating section having a pair of heating columns, wherein the pair of heating columns have a plurality of alternating rows of ducts. 
     
     
       7. The dryer of  claim 6  wherein the plurality of alternating rows of ducts have equal length air paths between an inner wall and an outer wall of the pair of heating columns.